1. Field of the Invention
This invention relates to an oil separator for separating lubrication oil from blow-by gas which comes to be produced in an internal combustion engine.
2. Description of the Background
In operation of an internal combustion engine, some parts of gas in the combustion chamber leak into the crank case through a gap between the piston and the cylinder during compression and explosion strokes. This "blow-by" gas contains some volume of lublication oil constituents.
There have been proposed many devices for separating these lubrication oil constituents from the blow-by gas. For instance, in the device disclosed in the Bulletin of the Japanese Utility Model Laid-open No. 149013/1981 (No. Jitsu-kai-sho 56-149013), an oil separation case is arranged in a cylinder-head cover; a zig-zag path for the blow-by gas is formed in the case by means of arranging baffle plates therein; and the oil constituents contained in the gas are separated by the function of the zig-zag path which makes the flow direction of gas change abruptly. That is to say, while the gas itself can change its flow direction smoothly, oil particles heavier than a certain degree cannot make a sudden change of its flow direction, and consequently, such oil constituents collide against the wall of the zig-zag path and adhere thereto. When the number of adhered oil constituents increase, they come to form drops and fall along the wall by their own weight. The blow-by gas from which the oil constituents are excluded is sent to an intake manifold.
However, in the above way for separation, the fog-like fine oil particles tend to pass through the zig-zag path with the gas. This makes it difficult to separate and collect oil constituents completly from the blow-by gas, and consequently, the lublication oil comes to flow into the intake manifold without being separated completely. It will be apparent that these tendencies cause a drawback in that the comsumption volume of lubrication oil becomes large and various sensors installed to the manifold are contaminated with oil.
One effective way to avoid the above inconvenience is to use a porous filter for absorbing the oil constituents. In accordance with such device, a porous filter made of foam metal is arranged vertically in the chamber for separation of oil. When the blow-by gas flows into the separation chamber and passes through the porous filter, the oil constituents in the blow-by gas are absorbed by the porous filter. The absorbed oil falls along the surface of the filter and is reserved for recycling it to the cylinder. The upper portion of the porous filter is maintained as a path for gas, as the oil adhered to this portion is excluded therefrom according to the fall of oil. This would be a very efficient way for separating oil from the blow-by gas.
However, in using the porous filter as a means for separating oil, there are still a possibility of inconvenience. For instance, the blow-by gas sometimes contains the constituents of some foreign materials. Such foreign constituents are also absorbed by the porous filter and might clog pores of the filter. If the path for the gas in the filter comes to be closed by such foreign constituents, the inner pressure of the crank case will increase extraordinarily and the blow-by gas will leak outside of the engine through sealed portions such as the gasket portion between the cylinder and the cylinder-head cover.